SSLV1.1 builds & fairy tales

[KevinHeem]

Feed them of raw DC across the reservoir capacitor

Boo Hoo that means taking the supplies out of the chassis.

 

[Salas]

There are exposed bridge diodes leads connected to the RAW+ and GND.
Locate what pad points you need with your DMM in DCV mode

 

[Tix88]

Hello Salas, I completed the circuit, but it does not work. The 4 green LEDs light up, but the remaining 2 red no, what should I check?

 

[Salas]

Proper dummy loading first. Not to choose a too heavy load value for the available CCS current at goal Vout. So to make sure the reg is not starved. By measuring voltage drop across R101 and dividing by R101's value you derive the CCS current available.

 

[Tix88]

The dummy load as per your advice 1k, connected to 4 wires

 

[Salas]

OK then with the dummy. Now measure voltage drop across R101 (or R301). So we know we have enough current. Then make sure the four wire connection to the dummy is correct by comparing to the wiring photo in the guide. If those two steps are good, then we will look in the red leds correct orientation, small transistors correct position and health, and in Mosfets health.

 

[Tix88]

The connection of the dummy load is ok, on the R301 it measures 3.8 VDC

 

[Salas]

If its 22 Ω then there is 170mA current available. I.e. good.

 

[Tix88]

Yes my r301 is 22Ω,
I need the shunt for a Pass B1, and datasheets consumes 0.02A

 

[Salas]

OK 150mA spare then. That's good enough, kinda hot-rod. Inspect for correct red leds orientation now. Also make sure there is a proper bridge in unused places of the voltage set components (in the see text outlined area). We want the voltage setting parallel leg unbroken.

 

[Tix88]

The LEDs are properly oriented, I have a bridge in place of the diode, as a guide.

 

[Salas]

But are they healthy too? When powered off, try with a 9V battery or a DMM in diode mode (some are able to drive a led some are not) to touch their legs and see if they light up. 3mm leds sometimes die in hot assembly.

 

[Tix88]

It is the LEDs work, it was the first thing I had tried

 

[Salas]

OK. Are the BC transistors in right places and do they show about 0.6V between b,e pins when the power is on? Do the output Mosfet show any voltage between g,s pins? Is there any voltage at the output at all?

 

[Tix88]

Thanks for the help Salas, you're very helpful, but I had not realized that the heat sinks of the FET touched and then went in short, is now fully functional, thanks a lot. I'm sorry if I made you waste time.

 

[Salas]

No worries. Congratulations for your success. Let us know how it went with your B1.

 

[Tix88]

Of course Salas, thanks so much

 

[Despearce]

I have a question about heatsink size and whether I should make some alterations.

I need 250mA and currently have 550mA CCS (measured voltage drop across R1 and divided by R1 value). is this too much, should I alter the value of R1? The heatsink on Q106 gets quite hot, I can touch it but it is at the upper limit of what I can comfortably touch for a couple of seconds (the baseplate it's touching gets warm for a few cm around the heatsink), do I need a bigger heatsink and would it hurt to get one say 120mm by 50mm by 50mm and have both Q101 and Q106 attached to it?

An externally hosted image should be here but it was not working when we last tested it.

 

[Salas]

Cut back 150mA and it should make quite a cool down difference as it is if you don't need more than 350mA peak for the load it feeds

*Instead of bigger heatsink, try direct mounting of Mosfets to the baseplate (keeping the Silpads) if its still too hot for your comfort

 

[Despearce]

so increase R1 to 30 Ohms should give me 400mA and decrease the temperature on Q106 heatsink?